Unloading device for compressors.



PATENTED MAR. 14, 1905.

F. W. PARSONS. UNLOADIN G DEVICE FOR GOMPRESSQRS.

APPLICATION FILED JAN. 28, 1902.

INVENTOR ATTORNEYS m! Mr K UNITED STATES Patented March 14, 1905.

PATENT OFFICE.

' FREDERICK IVILLIAM PARSONS, OF TARRYTOIVN, NEIV YORK, ASSIGNOR TO RAND DRILL COMPANY, OF NEW YORK, N. Y., A CORPORATION OF NEIV YORK.

UNLOADING DEVICE FOR COMPRESSORS.

SPECIFICATION forming part of Letters Patent No. 784,961, dated March 14, 1905.

Application fil d January 28, 1902. Serial No, 91,610.

To (LY/Z mini/n it may concern:

Be it known that 1, FREDERICK WILLIAM- PARSONS, a citizen of the United States of America, residing at Tarrytown, county of l/Vestchester, State of New York, have invented certain new and useful Improvements in Unloading Devices for Compressors, of which the following is a specification, reference being had to the accompanying drawings, forming a part thereof.

This invention relates to unloading devices, and particularly to that class of unloading devices which operate by controlling the supply of fluid to be compressed.

The invention consists in a fluidpressure operated means for controlling the supply, through the compressor inlet-valve, of fluid to be compressed, which is itself controlled by the movements of a separate and independent valve operated by variations in fluid-pressure.

The fluid-pressure which operates this lastnamed valve is preferably that in the receiver to which the compressor delivers.

The main object of the invention is to pro- 2 5 vide a simple and positive unloading device by which the admission of fluid to be compressed may be positively and entirely cut off when the pressure in the receiver to which the compressor delivers rises above a predetermined point and to freely admit fluid for compression when the pressure in the receiver falls below such point.

My invention further consists in certain details of construction and combination of parts,

3 5 as shall hereinafter be more fully set forth, and other objects ofmy invention will appear in the following specification.

1 will now proceed to describe an unloading device embodying my invention and will 4 then point out the novel features in claims.

In the drawings, Figure 1 is a view in side elevation of a compressor and an unloading device embodying my invention in connection therewith. Fig. 2 is a view in central verti- 4 5 cal transverse section of the unloading device.

The unloading device herein comprises a casing 1, having therein two cylindrical bores 2 and 3. The casing 1 has a chamber or passage 4 there-through atits upper end, to which passage fluid to be compressed is admitted through a connection 5 and from which It passes through a connection 6 to the inlet valve or valves of the compressor.

A fluid-pressure-operated means compris ing a piston-valve 7 is mounted in the bore 2 of the casing 1. The piston-valve is adapted to be moved in the bore and in its uppermost position to close the passage 4, and thereby to cut off the admission of fluid for compression. ,In its lowermost position, in which position it is shown in Fig. 2 of the drawings. free passage of fluid is allowed through the chamber or passage 4:. Another piston-valve S is mounted in the bore 3 and is arranged to be moved longi tudinally therein. One end of the cylindrical bore 3 is in open communication through a connection 9 with the receiver to which the compressor delivers. This bore 3 on the opposite side of the piston-valve is open to atmosphere through a discharge port or passage 10. An inlet port or passage 11 is arranged to connect the bore 2 with the bore 3, and an exhaust port or passage 12 is also arranged between the two said cylindrical borcs. A spring 13 operates to force the piston-valve 8 in one direction against the pressure in the said receiver to which the compressor delivers. hen the pressure in the said receiver rises above the predetermined point, it will overcome the tension of the spring 13, and the piston-valve 8, which up to such time had overridden the port or passage 11, so as to close same, and had left free communication from the cylindrical bore through the exhaust port or passage 12, will be moved forward to lirst close the said port or passage and then to open the inlet port or passage 11, so as to admit fluid under pressure into the cylindrical bore 2 behind the piston-valve '7. The said piston-valve will then be quickly raised, so as to close admission of fluid-supply, and the said piston-valve will remain in such a position to so close the supply until the fluidpressure in the receiver falls below the point at which the spring 13 will overcome same. I/Vhen the pressure so falls, the pistonvalve 8 will be returned to the normal position in which it is shown in Fig. 2 of the drawings, first overriding the port or passage 11, and thereby cutting oil admission of fluid-pressure to the cylindrical bore 2, and then uncovering the port or passage 12, so as to permit the discharge or exhaust of fluid from beneath the piston 7 through the said exhaust port or passage 12 and discharge passage 10. The piston-valve 7 will then fall to its normal position at the lower end of the cylindrical bore 2 by gravity or otherwise, as may be desired.

The provision 01" an independent valve, such as the piston-valve 8, operated by the variations in fluid-pressure in the receiver to which the compressor delivers, for controlling the movements of the liuid-pressure-operatcd means which controls the supply of fluid to be compressed will cause the device to operate positively at all times-that is to say, when the pressure in the receiver rises above a predetermined point admission will be entirely cut ofl, while when the pressure in the receiver falls below such point admission will be free and unobstructed. ll the valve 8 or its equivalent were omitted and connection were made directly from the receiver 4 to beneath the pressure-operated valve 7, the

valve 7 would be constantly in an intermediate position and. supply to the compressor would be restricted for some time prior to the entire closing of same, and considerable friction or wire-drawing would result.

The spring 13 may of course be set at any desired tension, so that the device may operate at any predetermined degree of pressure in the receiver, and for the purpose of so regulating the spring 13 an adjusting-screw 14 is provided.

it is obvious that many n'iodilications of the structure herein shown may be resorted to within the spirit and scope of my invention, and hence I do not desire to be limited only to the precise details and combination of parts herein set Forth.

hat I claim is 1. in an unloading device for compressors, the combination with a casing containing a fluid-pressure cylinder through one end of which air to be compressed passes to the compressor, of a combined piston and valve fitted to said cylinder and arranged in its movements to control passage of air therethrough, said cylinder provided at its end opposite the end through which said inlet-air passes, with inlet and exhaust ports, a secondary valvechamber, and a controlling valve therein, spring-actuated in one direction and arranged to be actuated by receiver-pressure in the opposite direction, said controlling valve arranged in its movements to control said inlet and outlet ports, substantially as specified.

2. An unloading device for compressors comprising a casing having therein a cylindrical bore closed at its lower end by a wall or diaphragm and at its upper end by a cap, through which latter end air to be compressed is arranged to pass, and having also another cylindrical bore which passes clear through the casing at substantially right angles to the lirst said bore, and immediately beneath same, and two passages through the wall or diaphragm between said bores and connecting same, one of said passages for inlet and the other for discharge, said last-mentioned bore having also an exhaust-passage, of a cap closing one end of said last-mentioned bore, means for connecting the opposite end thereof with the receiver of an air-compressor, a pistonvalve in said first-named bore, adapted when moved upwardly to close the air passage through the upper end thereof, a second pis ton in said last-named bore, said piston-spring actuated in one direction and open to receiverpressure to actuate it in the other, and adapted alternately according to its position to override one or other of said connecting-passages, and so to open the inlet-passage between the bores to receive the pressure, or to close same and open the discharge-passage to exhaust, substantially as specified.

In testimony whereof I aflix my signature in the presence of two witnesses.

FREDERICK llllllihlll PARSONS \Vitnesses:

A. H. PERLES, M. M. CoNovnR. 

